The Anglican Diocese of Sydney has donated $1 million to the "no" campaign in Australia's postal survey on same-sex marriage.

Archbishop of Sydney Glenn Davies announced the hefty donation in his address to the 51st Synod of the Diocese of Sydney on Monday afternoon.

He told the gathering that the diocese had been a founding member of the Coalition for Marriage, along with the Roman Catholic Archdiocese of Sydney, Marriage Alliance and the Australian Christian Lobby.

"The Standing Committee has also enthusiastically backed our participation in the Coalition For Marriage and has taken the bold step of drawing down one million dollars from the Diocesan Endowment to promote the 'no' case," he said.

Davies told the gathering that "the stakes are high and the cost is high".

"Yet the cause is just and it is a consequence of our discipleship to uphold the gift of marriage as God has designed it — a creation ordinance for all people. By so doing, the wisdom of God is made manifest."

A spokesperson for the diocese told BuzzFeed News the donation had been made to the Coalition for Marriage about a month ago. It is significant in the context of a campaign where neither side has been open about its finances.

What has been made public is that Qantas CEO Alan Joyce personally donated $1 million to the "yes" case last month, while the "no" campaign has had two anonymous donors matching donations up to $200,000 and $400,000 respectively.

Cameron Spencer / Getty Images

Both sides have sought to downplay how much money they are receiving. Damien Wyld, the CEO of Coalition For Marriage partner Marriage Alliance, said in a recent email sent after the diocese made its $1 million donation that the Coalition For Marriage didn't have the same money as the Equality Campaign.

"Some weeks ago, 'marriage equality' activist Tiernan Brady provided me with a good laugh. He said we had a 'huge bucket of cash'," he said.

"It sounded funny then. It sounded even funnier when Qantas CEO Alan Joyce tipped a cool million dollars out of his pay packet into the 'yes' campaign.

"We don't have that sort of funding at our fingertips."

Davies said in his speech that he made "no apology" for encouraging Australians to vote "no" in the survey.

"I believe that a change in the definition of marriage is unwarranted, not just because it is in opposition to the teaching of scripture and our Lord himself in Matthew 19," he said

"But because I believe marriage, traditionally understood as a union of one man and one woman, is a positive good for our society, where marriage and the procreation of children are bound together as the foundational fabric of our society, notwithstanding the sad reality that not all married couples are able to conceive."

Survey forms must be returned to the Australian Bureau of Statistics by November 7, with a result in the survey announced on November 15.

An ABS estimate released last Tuesday said 57.5% of Australians had already returned their forms. The next update from the ABS will be released tomorrow.

Lane Sainty is a reporter for BuzzFeed News and is based in Sydney, Australia.